I have in play Jughernaut of Khorne and seeking unit cost with 0 to put in play and attack. Can I trigger the JoK's action for free which says?

" Action: When this unit attacks, sacrifice X developments to search the top five cards of your deck for a unit with printed cost X or lower and put it into your battlefield, attacking. Then, shuffle your deck ."

Is that correct wouldn't sacrifice development, look the top five cards of my deck for a unit with 0 printed cost, then play this way in my battlefilde?

That's correct.

So if I have a Daemon Prince within my 5 searched cards can I play that card (cost 0) to my battlefield and attack with it even if says it can't be declared as an attacker till hasn't got three resources on it from sacrificing units. But in this matter I do not declare him just put in to play after the attackers already declared. ??? It can work this way?

That's how I would rule it. But I don't think it has ever been officially clarified that "put into play attacking / declared as an attacker" and similar effects do indeed circumvent "cannot be declared" effects.

Make it more wired. I have got two Scout Camps in my Kingdom as well. How does the JoK ability work with these Scout Camps which say:

"Kingdom. Whenever you search your deck, you may search an additional card."

Does it mean after when I've searched one card with JoK and shuffle my deck then I can search again and one more used the same searching condition what I've declared for the first search or I can declare new searching conditions for the searches?

Can I put even 3 Daemon Prince in attack in this way if I can "find" them ? Logically seems ok, isn't it?

Scout Camp increases the number of cards you search, not the number of cards you search for, or the number of searches. So if you use the Juggernaut's Action with two Scout Camps, you'll get to search the top seven cards of your deck once for one unit.

So you mean in the case of Necrodomo's Profecy the scout camps won't modify my searching condition at all?

" Action: Sacrifice a unit to search your deck for a [Chaos] card, reveal it, and shuffle your deck. Then, put that card on top of your deck ."

or the case of Ancient Map

" Action: Search your deck for a quest card, reveal it to each player, and add it to your hand. Then, shuffle your deck ."

My understanding is you can search an additional card in that another new search for a new additional card over the actioned one card search. So like repeated search.

???

Your understanding is wrong. Check the "Search" entry in the FAQ.

Your understanding is wrong. Check the "Search" entry in the FAQ.

Ok. I have the terminology of the "search" from FAQ.

" For example: Scout Camp (CC 60) reads, "Whenever you search your deck, you may search an additional card." This interacts with cards that specifically search your deck, like Runesmith Apprentice (EC 22), which reads, " Action: When this unit enters play, search the top five cards of your deck for any number of Rune cards, reveal them, and put them into your hand. Then, shuffle the remaining cards into your deck." If you played Runesmith Apprentice while a copy of Scout Camp was already in play, you would search the top six cards of your deck, instead of the top five."

So, than my question is how the Scout Camp affect the above mentioned "searches"? Or those searches are not searches? I cannot imagine an additional card search top of my whole deck.

When you search your whole deck, Scout Camp doesn't change anything. You definitely do not get to search an additional time.

When you search your whole deck, Scout Camp doesn't change anything. You definitely do not get to search an additional time.

Logically I do. Think about it. In the above examples actually you search your X top card of your deck, where X is the current number of your deck. So plus one additional card means my whole deck plus one card. Which is possible after the shuflle. But anyway it doesn't make any sence if I found already the card what I was looking for in my "previous search".

So I have to agree even if I am not happy with that.